The continuing trend of scaling down integrated circuits has motivated the semiconductor industry to consider new techniques for fabricating precise components at sub-micron levels. As is the case for most semiconductor integrated circuitry, circuit density is continuing to increase at a fairly constant rate and a major area of technological efforts is in fabrication processes to pattern contact locations for interconnection within the integrated circuitry. A typical nanometer lithography process may use a multi-layered resist process, such as a top photoresist layer and an anti-reflective coating. However, anti-reflective photoresist coatings used in the multi-resist process cannot be etched selective to materials used to form self-aligned contact locations during pattern transfer using a conventional anti-reflective coating etch as the etch will not only remove the anti-reflective coating but the underlying material (i.e., nitride) as well.
Typical multi-layered resist processing does not allow for the anti-reflective coating to be removed before complete pattern transfer from the multi-layered resist to the underlying material takes place. If the anti-reflective coating is not removed before complete pattern transfer, then problems will occur, two of which are: 1) when the anti-reflective coating is removed a partial pattern transfer will occur in the underlying materials and 2) the anti-reflective coating will lift off during subsequent removal of the remaining layers of the multi-layered resist.
For example, when employing a standard fabrication process to pattern multi-layered resist (i.e., a top photoresist layer and an anti-reflective coating), the anti-reflective coating is removed after an anti-reflective coating/carbon etch is performed. In this case, the anti-reflective coating etch has selectivity to the underlying material (i.e., nitride) and the anti-reflective coating. With the anti-reflective coating being present when the resist is stripped, the anti-reflective coating will peel off of the underlying carbon, which is a highly undesirable occurrence during the patterning stage as the desired pattern will be affected. Thus, conventional multi-resist processing using an anti-reflective coating, is not suitable for use in the formation of self-aligned contact openings (or vias) due to etch selectivity requirements to underlying materials.
What is needed is a method to successfully pattern and etch contact openings and ultimately to form self-aligned contacts therein, by using a multi-resist process, which employs anti-reflective materials, in order to achieve the nanometer line widths now being demanded in current and future semiconductor fabrication processes.